In recent times, the transportation industry has generated a number of developments involving new technology in
signaling. Important developments have involved the production of light by means of light emitting diode (LED). The
optical proprieties of LEDs depended on junction temperature. Since the heat from the junction must be dissipated into
the ambient somehow, changing the ambient temperature affects the junction temperature and hence the emitted light.
When the LEDs have been used in the railway or traffic signals, the optical proprieties of these have to maintain more
rigorous color specifications. Besides, the limits imposed must be respected in ample range of variation of the ambient
temperature (typ. 233-347K). The peak wavelength of LED shifts proportionally to changes in junction temperature.
Therefore, to respect color specifications with signals using LED as light source it is not simple. In this paper, we
describe problems of the temperature dependent changes of colorimetrical parameters of LEDs. Besides we will
introduce a method through which to build a correct signal with feedback that, according to the measured temperature, it
reacts to correct the optic characteristics of signal.
At present, the progress in optics is associated with wide use of diffractive optical elements (DOEs). In this paper we present a DOE design method, which not use computer iterative methods. Starting from the knowledge of the expression of the propagated field on image plane, we use simple formulas to obtain the entire information necessary to characterize the desired DOE. The DOE designed with the proposed method can equate an arbitrary complex amplitude transmission T(r) and has higher imaging accuracy than other DOEs. Even if it is possible studying any level combination, the aim of this paper is to summarize the results of simulation experiments which were carried out only to test the binary level diffractive optical elements (DOEs).
In recent times, the transportation industry has generated a number of developments involving new technology in signaling. Important developments have involved the production of light by means of light emitting diode (LED). Since the heat from the junction must be dissipated into the ambient somehow, changing the ambient temperature affects the junction temperature and hence the emitted light. When the LEDs have been used in the railway or traffic signals, the optical proprieties of these have to maintain more rigorous specifications. The junction temperature of the power LEDs affects the device's luminous flux of the device. In this paper, we describe problems of the temperature dependent changes of LED intensity. Besides we will introduce an innovative technical to allow the use of the LEDs in applications with rigorous specifications.
When we buy an artwork object a certificate of authenticity contain specific details about the artwork. Unfortunately,
these certificates are often exchanged between similar artworks: the same document is supplied by the seller to certificate
the originality. In this way the buyer will have a copy of an original certificate to attest that the "not original artwork" is
an original one. A solution for this problem would be to insert a system that links together the certificate and a specific
artwork. To do this it is necessary, for a single artwork, to find unique, unrepeatable, and unchangeable characteristics. In
this paper we propose a new lithography certification based on the color spots distribution, which compose the
lithography itself.
Due to the high resolution acquisition media available today, it is possible using analysis method typical of speckle
metrology. In particular, in verification phase it is only necessary acquiring the same portion of lithography, extracting
the verification information, using the private key to obtain the same information from the certificate and confronting the
two information using a comparison threshold. Due to the possible rotation and translation it is applied image correlation
solutions, used in speckle metrology, to determine translation and rotation error and correct allow to verifying extracted
and acquired images in the best situation, for granting correct originality verification.
Digital treatment of images has been widely used in many different fields, including astrophysical, medical, geographical
and military research. In the last years, digital elaboration of the images has also been used in the field of the Cultural
Heritage conservation. Many paintings, especially old ones, suffer from breaks in substrate, paint, or varnish. These
patterns are usually called cracks or craquelure and can be caused by aging, drying, and mechanical factors. The
appearance of cracks on paintings deteriorates the perceived image quality. However, one can use digital image
processing techniques to detect and eliminate the cracks on digitized paintings. Such a "virtual" restoration can provide
clues to art historians, museum curators and the general public on how the painting would look like in its initial state, i.e.,
without the cracks. An integrated methodology for the detection and removal of cracks on digitized paintings is
presented in this paper.
KEYWORDS: Digital watermarking, Image filtering, Computer generated holography, Image compression, Holograms, Digital imaging, Medical imaging, Holography, Image processing, Digital holography
Fragile watermark is designed to detect slight changes to the watermarked image with high probability. In the security community, an integrity service is unambiguously defined as one, which insures that the sent and received data are identical. This binary definition can also be applicable to images; however it is too strict and not well adapted to this type of digital document. Indeed, in real life situations, images will be transformed. Their pixel values will therefore be modified but not the actual semantic meaning of the image. In order to provide an authentication service for still images, it is important to distinguish between malicious manipulations, which consist of changing the content of the original image such as captions or faces, and manipulations related to the use of an image, such as format conversion, compression, filtering, and so on. Unfortunately this distinction is not always clear; it partly depends on the type of image and its use. Scope of this paper is to present potentiality of Holographic technique in fragile watermarking for digital image authentication of medical or military images.
In order to measure small diffusion coefficients of miscible fluids, in this paper we propose an improved version of digital projection moiré. The system uses a simple and flexible fringe generator realized by means of a video projector with a modification of projection optic. The fringe patterns are projected on the bottom of a ground glass plate. The phase object (diffusion cell) is placed in front of the ground glass (in other words, in front of the fringe pattern), which is imaged by a digital video camera. Grating patterns, during the evolution of diffusion phenomena, are captured by a CCD camera and stored in a computer at different times. With the aid of signal demodulating techniques, the images are processed to obtain the diffusion coefficients. The theoretical aspects of the method are presented and the relationship between the fringe shift and the diffusion coefficient is derived. Furthermore, we report some experiments conducted for demonstrating the usefulness of the system.
KEYWORDS: Digital watermarking, Computer generated holography, Digital imaging, Image compression, Medical imaging, Image filtering, 3D image reconstruction, Image processing, Computer programming, Digital holography
In this paper we propose a fragile marking system based on Computer Generated Hologram coding techniques, which is able to detect malicious tampering while tolerating some incidental distortions. A fragile watermark is a mark that is readily altered or destroyed when the host image is modified through a linear or nonlinear transformation. A fragile watermark monitors the integrity of the content of the image but not its numerical representation. Therefore the watermark is designed so that the integrity is proven if the content of the image has not been tampered. Since digital images can be altered or manipulated with ease, the ability to detect changes to digital images is very important for many applications such as news reporting, medical archiving, or legal usages. The proposed technique could be applied to Color Images as well as to Gray Scale ones. Using Computer Generated Hologram watermarking, the embedded mark could be easily recovered by means of a Fourier Transform. Due to this fact host image can be tampered and watermarked with the same holographic pattern. To avoid this possibility we have introduced an encryption method using a asymmetric Cryptography. The proposed schema is based on the knowledge of original mark from the Authentication
The determination of the sequence of line crossings is still a current problem in the field of forensic documents examination. This paper presents the potentiality of the 3D micro-topography to resolve the writing order of signatures (if partially superimposed), to detect the tampering of manuscripts (if the added inscription superimposes itself on parts already written), to analyze pressure variation, and to identify strokes in handwritten. The system used, in this paper for creating 3D micro-topography, is based on conoscopic holography. It is a non-contact three-dimensional measuring system that allows producing holograms, even with incoherent light, with fringe periods that can be measured precisely to determine the exact distance to the point measured. This technique is suitable to obtain 3D micro-topography with high resolution also on surfaces with unevenness reflectivity (which is usual on the surface of the handwritten document). The proposed technique is able to obtained 3D profile in non-invading way. Therefore, the original draft do not be physically or chemically modified, allowing the possibility of multi-analysis in different time, also in case of forensic analysis with the necessity to preserving the original sample. The experiments performed with line crossings data base show that the proposed method is able of "positive identification" of writing sequence in the majority of the tests. When we have not had a positive identification, the result has been "inconclusive". The proposed technique, if correctly used, does not supply "false positive" or "probable" identifications. The possible results are only: "positive identification" and "inconclusive".
In this article is presented an application of synthetic hologram as fragile watermarking. The proposed technique is a frequency domain watermarking, based on computer generated hologram. Our technique, named Fragile Synthetic Holographic Watermarking (F-SHW), is suitable for ID Cart image authentication. In this paper, the F-SHW is applied to Color Images as well as to Gray Scale ones. The proposed schema is based on the knowledge of original mark from the Authentication Entity, for applying Image Correlation between this and the extracted one. Due to the application the mark is encrypted using a private key (symmetric schema).
KEYWORDS: Cultural heritage, 3D acquisition, 3D modeling, Visualization, 3D scanning, Holography, 3D image processing, Lithium, Electronic imaging, Internet
One of the most powerful applications of the World Wide Web (WWW) is the storage and distributuion of multimedia, integrating text, images, sound, videos and hyperlinks. In cultural heritage this is of particular interest, because best methods to convey a complex knowledge in the field of cultural heritage, to experts and non-experts, are the visual representation and visual interaction.
In this work we propose 3D acquisition and digitizing techniques for the virtualized reality of small cultural heritage objects (virtual gallery). The system used for creating 3D shape is based on the conoscopic holograph. This technique is a non-contact three-dimensional measuring technique that makes possible to produce holograms, even with incoherent light, with fringe periods that can be measured precisely to determine the exact distance to the point measured. It is suitable to obtain 3D profile with high resolution also on surface with unevenness reflectivity (this situation is usual on the surface of the cultural heritage objects). By conoscopic holography, high-resolution 3D model can be obtained. Howver, accurate representation and high-quality display are fundamental requirements to avoid misinterpretation of the data. Therefore, virtual gallery can be obtained through a procedure involving 3D acquisition, 3D model and visualization.
In studying hydrodynamic instabilities between two miscible fluid mixtures, one often faces the problem of assigning a reliable value to very small diffusion coefficients. It is also difficult that for diffusion between two binary mixtures, such as water and glycerin, water and salt, etc., no complete data are available in the literature. To measure the isothermal diffusivity of liquid binary mixtures, we propose an improved version of digital projection moiré. The system uses a simple and flexible fringe generator realized with a diffractive optical element (DOE). The fringe patterns are projected onto the bottom of a ground glass plate. The phase object (diffusion cell) is placed in front of the ground glass (in other words, in front of the fringe pattern), which is imaged by a digital video camera. Grating patterns, during the evolution of diffusion phenomena, are captured by a charge-coupled device (CCD) camera and stored in a computer at different times. With the aid of fast Fourier transform (FFT) and signal demodulating techniques, the images are processed to obtain the diffusion coefficients. The theoretical basis of the technique is presented. We also report experiments conducted for validating the system.
We propose an optical method to evaluate deterioration mechanisms affecting cultural heritage materials. The method is based on a phase element, which forms interference fringes on the object. The surface topography is obtained by a phase shifting technique.
In studying hydrodynamic instabilities between two miscible fluid mixtures one often faces the problem of assigning a reliable value to very small diffusion coefficients. As for diffusion between two binary mixtures such as water and glycerin, water and salt, etc., no complete data are available in the literature. In order to measure small diffusion coefficients of miscible fluids, in this paper we propose an improved version of digital projection moire. The system uses a fringe generator realized with a diffractive optical element (DOE). The fringe patterns are projected on the bottom of a ground glass plate. The phase object (diffusion cell) is placed in front of the ground glass (in other words, in front of the fringe pattern), which is imaged by a digital video camera. Grating patterns, during the evolution of diffusion phenomena, are captured by a CCD camera and stored in a computer at different times. With the aid of Fast Fourier Transform (FFT) and signal demodulating techniques, the images are processed to obtain the diffusion coefficients. The theoretical basis of the device is presented. Furthermore, we report some experiments conducted for demonstrating the usefulness of the system.
In this paper we present an unwrapping weighted algorithm to analyze phase maps obtained by fringe projection 3-D profilometry.
Phase unwrapping is a critical step in any phase measurement technique in which the height of an object is obtained from phase data. Indeed, when a complex object is measured, abrupt and irregular changes in the measured surface may result in local shadows. In shadow areas the observed phase data are uncertain or misleading. These zones yield “lacunae”, in the reconstruction of the 3D model.
In this work we propose a new phase unwrapping method able to mitigate the “lacunae” problem by interpolation of phase data.
The case of an image containing regions without phase information is treated, in our algorithm in the following manner: (a) phase inconsistencies are handled by excluding invalid pixels from the unwrapping process though the assignment of zero-valued weights; (b) an unwrapped phase map is obtained by an algorithm based on robust, path-independent method of phase unwrapping; (c) the lacks (zones of phase inconsistencies) are eliminated by means of an suitable procedure of interpolation; (d) a rewrapping procedure is used to obtain wrapped phase map without initial inconsistencies; (e) a new unwrapped phase map is obtained by the same algorithm used in step-b but with weights different from zero. The robustness of the proposed phase-unwrapping method is then tested computationally and experimentally and its enhancement is proven through the simulation and experimental results.
KEYWORDS: 3D modeling, Holography, 3D acquisition, Crystals, Visualization, Data modeling, Virtual reality, Holograms, Digital holography, Reflectivity
Physical access to historic and artistic manufactures can be limited by a lot of factors. In particular, the access to the collection of the ancient coins is difficult, especially for students. Indeed, for coins digital archive of high quality three-dimensional model and remote fruition is of great interest. In this work we propose 3D acquisition and digitizing techniques for the virtualized reality of ancient coins (virtual gallery). The system used for creating 3D shape of coins is based on conoscopic holography. This technique is a non-contact three-dimensional measuring technique that makes possible to produce holograms, even with incoherent light, with fringe periods that can be measured precisely to determine the exact distance to the point measured. It is suitable to obtain 3D profile with high resolution also on surface with unevenness reflectivity (this situation is usual on the surface of the ancient coins). By conoscopic holography, high-resolution 3D model can be obtained. However, accurate representation and high-quality display are fundamental requirements to avoid misinterpretation of the data. Therefore, virtual galleries can be obtained through a procedure involving 3D acquisition, 3D model and visualization. In conclusion, we propose an optoelectronic application, integrated with multimedia techniques, in order to improve the access to collection of ancient coins belonging to museums or privates.
Today, the vibration analysis of laminated structures represents an important field in engineering metrology. The experimental measurement of the resonant frequencies for the piezoceramic material is generally performed by impedance analysis. However to perform full-field, non-contact, and real-time measurement, optical methods are a preferable choice.
Recently, interesting results have been obtained by Electronic Speckle Pattern Interferometry (ESPI). In this paper, we report an alternative electro-optical system based on local digital speckle correlation. This new method permits the development of an instrument that is cheap, safe and easy to use. We employ the proposed method to investigate the vibration characteristics of piezoceramic/nickel-alloy laminated plate. The circular membrane is a composite made of a nickel alloy disk with thickness 0.1 mm and diameter 30 mm, to which a piezoceramic disk, with the same thickness and a smaller diameter (24 mm) is bonded. A brief analysis of the technique and some experimental results are presented. Finally, the numerical finite element calculation is also performed, and the results are compared with the electro-optical measurements.
Electronic Speckle Pattern Interferometry (ESPI) is a well-known tool in cultural heritage diagnostics. It can also reveal cracks and debonding of tiles in ancient mosaics of roman and medieval age. This paper describes a portable electro-optic system (it integrates the ESPI and local speckle correlation techniques) as a diagnostic tool to evaluate the state of conservation of ancient mosaic. Some experiments are been carried out on real, ancient, mosaics in laboratory and in situ.
Today, the vibration analysis of laminated structures represents an important field in engineering metrology. To perform non-invasive vibration measurements in industrial environments, optical methods are a preferable choice. Electronic Speckle Pattern Interferometry is a method, which permits full field and non-contacting displacement or deformation measurements. The experimental measurement of the resonant frequencies for the piezoceramic material is generally performed by impedance analysis. In this work, Electronic Speckle Pattern Interferometry (ESPI) technique is proposed for studying vibration of piezoceramic/nickel circular laminated plates. The circular membrane is a composite made of a nickel alloy disk with thickness 0. 1 mm and diameter 32 mm, to which a piezoceramic disk, with the same thickness and a smaller diameter (24 mm) is bonded. The time average frame subtraction technique is improved by subtracting two Bessel fringe patterns at two different amplitude levels. A brief analysis of the techniques and some preliminary experimental tests are presented.
Scientific investigation methods are founding their place besides the stylistic-historical study methods in art research works. In particular, optical techniques, transferred from other fields or developed ad hoc, can make a strong contribution to the safeguarding and exploitation of cultural heritage. This paper describes the use of different optical techniques, such as holographic interferometry, decorrelation, shearography and ESPI, in the diagnostics of works of art. A comparison between different methods is obtained by performing tests on specially designed models, prepared using typical techniques and materials. Inside the model structure, a number of defects of known types, form and extension are inserted. The different features of each technique are outlined and a comparison with IR thermography is also carried out.
A new non contacting, full field, variable sensitivity optical method is proposed for an experimental analysis of the local amplitude vibration of a diffuse surface. It is based on sinusoidal fringe projection interferometer just developed for contour map. Linear sinusoidal fringes, which are formed by the interference of two wave fronts emitted from the output of a fiber coupler, are projected on the object surface. The visibility of these fringes is modulated by a function of local amplitude of vibration; thus loci of constant vibrational amplitude can be directly observed as regions of high or low fringe visibility in the image of the surface. A brief analysis of the technique and some preliminary experimental tests are presented.
A contouring technique, based on digital speckle pattern interferometry, is developed for investigation of surface defects in artwork deterioration studies. Skeletonized fringes are used for a quantitative automatic evaluation of the defect dimension. Some experimental tests effected on samples and ancient artworks have demonstrated the suitability of the method.
A contouring technique based on digital speckle pattern interferometry is developed for investigation of surface defects in deterioration studies. A specific software is proposed for an automatic quantitative evaluation of defect dimensions. Some experimental tests effected on laboratory samples have demonstrated the suitability of the method.
An electro-optical system for the detection and quantitative measurements of surface or subsurface defects is presented; it is based on a holographic contouring technique and digital image processing for an automatic analysis of fringe patterns. Several approaches have been followed on models, so that the defects can be unambiguously detected and possibly quantitatively analyzed. Some examples of applications in deterioration investigations of ancient artworks are reported.
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